# System Fw

System $$F_\omega$$ is a system of higher-kinded types and type-constructors. It is relevant to compiling SML in the way that it relates to the module system. If we extend the kind system of "true" $$F_\omega$$ with product kinds, we might represent the module signature

sig
type t
type 'a u
end


as the kind $$* \times (* \rightarrow *)$$, and so on. This even extends to functors that act on modules via type-level lambdas.